CHM1 20WorkedProblem Collection

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Solution The half-equations are

Zn ? Zn²⁺             oxidation—loss of electrons

2Fe³⁺ ? 2Fe²⁺      reduction—gain of electrons

Since zinc metal (Zn) has donated electrons, we can identify it as the reducing agent. Conversely, since iron(III) ion (Fe³⁺) has accepted electrons, we identify it as the oxidizing agent. An alternative method of identification is to note that since zinc has been oxidized, the oxidizing agent must have been the other reactant, namely, iron(III). Also, since the iron(III) ion has been reduced, the zinc must be the reducing agent. Observe also that both the oxidizing and reducing agents are the reactants and therefore appear on the left-hand side of an equation.